added submodule update hint to README.md
added submodule update hint to README.md

[ci skip]

aina1205/nmtrypi-seek,aina1205/nmtrypi-seek,HITS-SDBV/nmtrypi-seek,aina1205/nmtrypi-seek,HITS-SDBV/nmtrypi-seek,HITS-SDBV/nmtrypi-seek,aina1205/nmtrypi-seek,HITS-SDBV/nmtrypi-seek